From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id DEB25606A31A for ; Thu, 29 Oct 2026 20:42:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=odGKC4Xb Received: by kanga.kvack.org (Postfix) id 164E26B05E9; Thu, 29 Oct 2026 16:42:38 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 13CB56B05EA; Thu, 29 Oct 2026 16:42:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 052A86B05EB; Thu, 29 Oct 2026 16:42:38 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id D9C8E6B05E9 for ; Thu, 29 Oct 2026 16:42:37 -0400 (EDT) Received: from smtpin25.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 7051E140476 for ; Thu, 29 Oct 2026 20:42:37 +0000 (UTC) X-FDA: 85376837154.25.9DA4408 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf29.hostedemail.com (Postfix) with ESMTP id BCFFC120006 for ; Thu, 29 Oct 2026 20:42:35 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=odGKC4Xb; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf29.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793306555; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=GzohAuTFTF3f/1hrG58iOYYkxgWAfRYzNd87kJom8ew=; b=udIM+XwWPXVDIePivo/nMR2wjvZy05IxM+fpZl+nG8YGgFEkRDrtExS0JL4XWjf0JU04lK C6MSXr2KOwhV0D9e3NnodjPOoBgL2H0PZ+UI54B0qZZeVOWBwHIOrPEASf343aHbJOcdKY rv1AQ3Me5Z3uOnV/pjgDG12h8ylirzs= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=odGKC4Xb; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf29.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793306555; b=Gr4fUNB/4BkigJBumXDsBU18TxCk09OEkaI7vYSNDbdljnyjTE+tsNkP6BtFwrJCDhwU94 2f5q4sy79AtYhAkKsxWGTbhcETcCVl9Y/G+KQgsBXYo6cfm9EM9hagrEn6OlL0yc7PnzSm OxD0w4AloN3KYE7IwoU4RSnnR9yinE0= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 4A1F7601EE; Thu, 29 Oct 2026 20:42:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 038A81F01816; Thu, 29 Oct 2026 20:42:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793306555; bh=GzohAuTFTF3f/1hrG58iOYYkxgWAfRYzNd87kJom8ew=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=odGKC4XbmYtEAL0Gbsmsvx/WY4VvPYy77ntTduDNGVxTee9x8eCFs1dlirZrbm7zy iC+kt5OPi0b7fGJlGk807OCvIbOWr/Z78TV/dFDtdfnfrPq2aHFVXyMPhLCSOvB1Y2 ZrN4hFhr9U2G7pJPJRhXKDaX8gWNjGlvbNVUoesFXn/q0rr+u58Qom2mW6f0Q09dKe 3q0AyCRIpFeQddnbKDlVIMB1qh/ZQ3BtSWnCL5WPB7IN9/D8mom8vqt7yZu9Csa5jg BDnVwDUFvXRY6YrP7saZiBtyJiwIROc+tG9ELKoNHPe8loZEUzoVScdiDJdLpehZRi /RsACXHCoLgfQ== From: "David Hildenbrand (Arm)" Date: Thu, 29 Oct 2026 21:33:32 +0100 Subject: [PATCH v2 37/47] mm: fix unkillable fault loop on MAP_DROPPABLE memory X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261029-fixes_core-v2-37-a64ce7f83abb@kernel.org> References: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> In-Reply-To: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> To: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, Chris Mason , stable@vger.kernel.org, "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1687; i=david@kernel.org; h=from:subject:message-id; bh=yoxwQ2Y6qIbeUiwHGT1Y0HumpGAEonmZ/vQerxKuLzY=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLIer+3czvM5O0THx//vtoUbudj7mWSPupTa/Tnr4Jkd8 Tn+Vk51RykLgxgHg6yYIktQ8H2Dly/X1Va78THDzGFlAhnCwMUpABNZl8XI8FEnafGyvrx5M6Kn sCw4PefgS4/ySwEXYgxE4k5desdXsorhf+JjyZr1Ze+2Bc4VtlpxsJI/8JO19IGImflnzH06jdO qmAE= X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A X-Rspamd-Queue-Id: BCFFC120006 X-Stat-Signature: y61b679atyc1b86cjogck3swm6wjdb7x X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=4.0.1 X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1793306555-742289 X-HE-Meta: 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 u5+IiXhx k3m+dNL2JcaJ1wd971DsNSjinEv4Gl2G2wrKduJJ2tsP4miAwF2ecsbj9BgpHzR3T6ZErooEcFENTxGOpG+LGiw+6MjibqaMMRLJ8dL6Pab14jWTz/BXSe2noMdXVY363tJ1XvEfJqlP0rWNLZgnhVOT/dZ4Wx/UsvIK/3BnLeOuQ4XGwiiPCQJBzUbWF5bw/4ps1xVp9dPlowgrw93UQqeAMO+E4kpjnbIUdYDn5iWn35aPJJRlMDDiEAxSZJa8KrxjIhrvJlAd6pHFgVKUhYLzCKx7u376EbQhQ+Rry/U1kx9UYXY4L4xf/qZ2gwwUW55zaiqEDBuTQlUuq3NKodNMIhjkxH03S2sVSaowwuAx8RDQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 From: Chris Mason handle_mm_fault() suppresses VM_FAULT_OOM for VM_DROPPABLE mappings. For user-mode faults, pending signals are processed before retrying the access. Kernel-mode faults on user buffers instead return directly to the faulting instruction. With persistent allocation failures (esp. memcg limits), a syscall, such as write(), can therefore loop while not dropping locks. Only suppress VM_FAULT_OOM when FAULT_FLAG_USER is set, allowing kernel-mode faults and GUP to fail and signal allocation errors. Fix generated by an LLM and sent by Chris Mason in private. Fixes: 9651fcedf7b9 ("mm: add MAP_DROPPABLE for designating always lazily freeable mappings") Cc: stable@vger.kernel.org Signed-off-by: Chris Mason Reviewed-by: Lorenzo Stoakes (ARM) [ david: simplify description ] Signed-off-by: David Hildenbrand (Arm) --- mm/memory.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 732b8f926de6..77d4bbf444bc 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -6957,8 +6957,12 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address, lru_gen_exit_fault(); - /* If the mapping is droppable, then errors due to OOM aren't fatal. */ - if (is_droppable) + /* + * If the mapping is droppable, then errors due to OOM aren't fatal: the + * task returns to user mode, handles its signals and tries again. A + * fault from kernel mode has no such return, so it must see the error. + */ + if (is_droppable && (flags & FAULT_FLAG_USER)) ret &= ~VM_FAULT_OOM; if (flags & FAULT_FLAG_USER) { -- 2.43.0